1. Field of the Invention
The present invention relates, generally, to clutch assemblies and, more specifically, to a one-way clutch assembly having an integrated damping feature.
2. Description of the Related Art
Generally speaking, land vehicles require three basic components. These components include a power plant (such as an internal combustion engine), a power train and wheels. The power train""s main component is typically referred to as the xe2x80x9ctransmission.xe2x80x9d Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. Transmissions include one or more gear sets, which may include an inner gear, intermediate planet or pinion gears which are supported by their carriers, and outer ring gears. Various components of the gear sets are held or powered to change the gear ratios in the transmission.
One-way clutches are frequently employed in transmissions, transfer cases, and differentials to selectively transmit torque in one rotational direction, but not in the opposite rotational direction. To this end, one-way clutches typically include an inner race, an outer race, and an engagement mechanism disposed therebetween. The inner race is typically splined to a shaft or hub and the outer race is often connected to a transmission case, clutch hub, or stator assembly via splined connection. The engagement mechanism is operable to lock the inner and outer races together thereby transmitting torque in one relative direction. The engagement mechanism is further operable to allow freewheeling rotation between the inner and outer races in the opposite rotational direction. Engagement mechanisms commonly used in one-way clutches of the related art include pawls, sprags, and rollers. A cage, along with biasing members, such as springs, are also sometimes employed to retain the pawls, sprags, or rollers between the inner and outer races as well as to selectively assist in the change of operational modes between torque translation and freewheeling actuation of the clutch, depending on the direction of rotation between the inner and outer races.
As noted above, one-way clutches of this type have been employed in numerous applications in transmission, transfer cases, and differentials. For example, one-way clutches have been employed in conjunction with multiple friction clutches and planetary gear sets to effect low and reverse gear ratios in conventional transmissions. One-way clutches have also been employed in transfer cases that provide full time, part time, and xe2x80x9con demandxe2x80x9d four wheel drive (4WD) capabilities. In these situations, the one-way clutch is typically disposed between the primary driveline and the secondary driveline. When the primary drive line attempts to over speed the secondary drive line, as will occur, for example, where the rear wheel is supported on a slick surface, such as ice and is spinning and the front wheels are solidly supported, the one-way clutch engages and transfers torque to the slipping wheel. In this way, 4WD is achieved, but in this case, only under circumstances that require it.
The one-way overrunning clutches of the related art are, for the most part, designed to be self-actuating. Thus, the clutches are designed to automatically shift between a locked-up mode wherein the inner and outer races are either held stationary or rotate together and a freewheeling mode wherein the inner and outer races freely rotate relative to one another. While the one-way clutches known in the related art have generally worked well for their intended purposes, they also have certain physical limitations and drawbacks.
For example, the inner and outer races may have to rotate over a relatively large angular distance while transitioning from the freewheeling mode to the locked-up mode. This angular distance is generally,referred to in the related art as xe2x80x9cbacklash.xe2x80x9d Backlash can result in unacceptable levels of noise and vibration as the engagement mechanism is deployed for torque translation between the inner and outer races. Generally speaking, the greater the backlash or angular distance traveled before engagement, the greater the noise and vibration generated during the transition from freewheeling to locked-up modes. Thus, excessive backlash causes undesirable driveline vibration and noise and ultimately results in a reduction in mechanical life due to the sometimes severe, repetitive impact forces that are generated during the operation of a one-way clutch employed, for example, in an automotive driveline
Accordingly, there remains a need in the art for a one-way clutch that is capable of efficiently, effectively, and smoothly transitioning between a freewheeling mode of operation and a locked-up mode of operation. In addition, there remains a need in the art for such a one-way clutch that also dampens or attenuates the noise and vibration that are generated during this transition using clutches known in the related art.
The disadvantages in the related art are overcome in the clutch assembly of the present invention having an inner race, an outer race, and an engagement mechanism disposed between the inner and outer races. The engagement mechanism is operable to move between a disengaged position wherein the inner and outer races may freely rotate in one direction relative to one another and an engaged position wherein in the inner and outer races are locked so as to translate torque therebetween in the opposite rotational direction. The inner race is defined by a plurality of plates and layers of elastomer that are disposed between adjacent plates in laminated fashion. The inner race further includes at least one bearing surface through which a force may be translated. The bearing surface is defined by a plurality of plates that are offset relative to an adjacent plate by a predetermined distance. The elastomeric layer allows movement of the offset plate in the direction of a force acting on the bearing surface such that the offset plates and the elastomeric layers act to absorb energy and dampen noise and vibration when the bearing surface is subjected to a force.
Alternatively, or in addition to the laminated inner race, the outer race may similarly be defined by a plurality of plates and layers of elastomer that are disposed between adjacent plates in laminated fashion. The outer race may therefore include at least one bearing surface through which a force may be translated. The bearing surface is defined by a plurality of plates that are offset relative to an adjacent plate by a predetermined distance. The elastomeric layer allows movement of the offset plate in the direction of a force acting on the bearing surface such that the offset plates and elastomeric layers act to absorb energy and dampen noise and vibration when the bearing surface is subjected to a force.
In this way, even in circumstances where the clutch assembly includes a certain amount of xe2x80x9cbacklash,xe2x80x9d the bearing surfaces on the inner and/or outer races act to dampen or attenuate the noise and vibrations that are generated when the clutch is transitioned between its overrunning or freewheeling mode to its locked-up mode. Furthermore, the bearing surfaces may be formed on any suitable force transmitting surface or surfaces located on the inner and/or outer race. Accordingly, the bearing surfaces may be located at the inner splined surface of the inner race, the teeth formed on the outer circumference of the inner race, at strategic locations formed in the pocket defined on the inner circumference of the outer race as well as the outer splined surface of the outer race. Furthermore, those having ordinary skill in the art will appreciate that the bearing surface is not required to be deployed on every force transmitting surface of the clutch assembly but may be strategically employed at selective location to attenuate noise and vibration that is generated during normal operations of a one-way, overrunning clutch assembly. In this way, the one-way clutch assembly of the present invention is capable of efficiently, effectively, and smoothly transitioning between a freewheeling mode of operation and a locked-up mode of operation while, at the same time, reducing or dampening the noise and vibration that is generated during this transition.